#include<iostream>
using namespace std;
 class student{
     string name,subject;
     int marks;
public:
   student(string n,string s,int m){
       name=n;
       subject=s;
       marks=m;
   }
   void displayGrade(){
       if(name.empty()||subject.empty()||marks<0||marks>100){
           cout<<"Invalid input";
           return;
       }
      char grade;
      if(marks>=90) grade='A';
      else if(marks>=75) grade='B';
      else if(marks>=50) grade='C';
      else grade='F';
      
      cout 
       <<"Name: " <<name << "\n";
       <<"Subject: "<<subject<< "\n";
       <<"Marks: " <<marks << "\n";
       <<"Grade: " <<grade;
   }
 };
int main(){
    string name,subject;
    int marks;
    getline(cin,name);
    getline(cin,subject);
    cin>>marks;
    student s(name,subject,marks);
    s.displayGrade();
    return 0;
}